The present invention relates to wearable infusion devices and more particularly to such devices that enable liquid medicaments to be conveniently and safely self-administered by a patient. One liquid medicament that is often self-administered by a patient is insulin, and for ease of description, the administration of insulin is generally used herein for exemplary purposes although the invention should not be limited by that exemplary use.
Administration of insulin has traditionally been accomplished using a syringe. Recently, needle carrying pen-like devices have also been employed for this purpose. Both forms of insulin administration require the patients to stick themselves each time they inject insulin, often many times a day. Additionally, a new clean needle must be mounted on the device each time they are used, and disposed of after each use, creating the additional problem of having the “sharps” with them whenever the patient needs to administer insulin, and to safely dispose of them after each use. Thus, these traditional forms of insulin administration have been a rather pervasive intrusion in the lives and routines of the patients who have had to adopt and employ them.
More recently, insulin pumps attached by tubing to an infusion set mounted on the patient's skin have been developed as an alternative form of insulin administration. Such pumps may be controlled by a programmable remote electronic system employing short range radio communication between a control device and electronics that control the pump. While such devices may involve fewer needle sticks, they are expensive to manufacture. They are also complex to operate and cumbersome and awkward to wear. Further, the cost of such devices can be many times the daily expense of using a traditional injection means such as a syringe or an insulin pen.
Devices of the type mentioned above also require a significant amount of training to control and thus use the devices. Great care in programming the devices is required because the pumps generally carry sufficient insulin to last a few days. Improper programming or general operation of the pumps can result in delivery of an excessive amount of insulin which can be very dangerous and even fatal.
Many patients are also reluctant to wear a pump device because they can be socially awkward. The devices are generally quite noticeable and can be as large as a pager. Adding to their awkwardness is their attachment to the outside of the patients clothes and the need for a catheter like tubing set running from the device to an infusion set located on the patient's body. Besides being obvious and perhaps embarrassing, wearing such a device can also be a serious impediment to many activities such as swimming, bathing, athletic activities, and many activities such as sun bathing where portions of the patient's body are necessarily uncovered.
In view of the above, a more cost effective and simple device has been proposed whereby an injection system is discreetly attached directly to the skin of the patient. One example of such a device is described in detail in U.S. application Ser. No. 12/147,283 filed Jun. 26, 2008 and titled DISPOSABLE INFUSION DEVICE WITH REDUNDANT VALVED SAFETY, which application is owned by the assignee of this application and incorporated herein by reference in its entirety. Such a device may be attached to the patient under the patient's clothing to deliver insulin into the patient by the manual pumping of small doses of insulin out the distal end of a temporarily indwelling cannula that is made a part of the pump device. The device may be made quite small and, when worn under the clothes, entirely unnoticeable in most social situations. It may still carry sufficient insulin to last a patient several days. It can be colored to blend naturally with the patient's skin color so as not to be noticeable when the patient's skin is exposed. As a result, insulin for several days may be carried by the patient discreetly, and conveniently applied in small dosages after only a single needle stick. For another description of devices of this type, reference may also be had to co-pending application Ser. No. 11/906,130, filed on Sep. 28, 2007 for DISPOSABLE INFUSION DEVICE WITH DUAL VALVE SYSTEM, which application is owned by the assignee of this application and hereby incorporated herein by reference in its entirety.
Although relatively discrete, the patient may have a reason to remove the system entirely. Likewise, if the drug delivery system is accidentally dislodged from the patient, it would be advantageous to be able to salvage the medicament and pump, and to replace only the minimum amount of the system. Where the pump, insulin supply and cannula are integral and non-separable units, removing just the pump or just the insulin, or adding a different liquid medicament is not generally feasible. Sometimes it would be advantageous to be able to remove the pump unit, the insulin reservoir, or the entire device, and to reassemble and use parts of the drug delivery system. Additionally, since the portion of system that contains the cannula needs to be removed and reinstalled every three days pursuant to current medical and regulatory practice, it would be advantageous to be able to remove the other portions of the drug delivery system from the portion with the cannula, and reattach them to a new cannula containing portion, thus avoiding replacing them with every use.
Further, it would be advantageous if the device was configured to utilize commercially available reservoirs or cartridges. It would be further advantageous if the reservoirs could be prefilled, releasing the patient from the task of filling the reservoir before the device is deployed on the patient's skin.
Unfortunately, shelf life becomes a problem with prefilled reservoirs. Most drug degradation is due to loss of moisture vapor. In order to assure adequate shelf life of a reservoir filled with insulin, for example, the reservoir materials and construction must minimize loss of moisture vapor. The present invention addresses these and other issues.